It is known to use a capacitative probe to measure liquid level. See, for example, “Digital Liquid Level Sensing Apparatus”, Hannan et al. (U.S. Pat. No. 6,125,696). However, such methods are dependent upon the dielectric constant of the liquid involved. Furthermore such measuring devices can electrically short out due to conductive internal structures. Also, capacitative probes often do not provide the accuracy that is required in various applications.
One of the problems associated with measuring the height of a liquid in a vessel using an electrical property of the liquid is that different liquids can have widely different conductivities (ability of a material to conduct an electric current) and the conductivity of the same liquid can vary depending upon its temperature. It would be desirable to use the electrical property of the liquid to accurately measure the height (which in turn can be used to determine other properties of the liquid, e.g., volume and weight) of the liquid in the vessel regardless of the conductivity or temperature of the liquid in the vessel.